A SIMPLE METHOD FOR THE CLASSIFICATION OF 

 BACTERIA AS TO DIASTASE PRODUCTION 



PAUL W. ALLEN 



Dairy Bacteriology Laboratory, University of Illinois 



Received for Publication May 25, 1917 



Among the various physiological reactions selected by the 

 Classification Committee of the Society of American Bacteri- 

 ologists for determining the identity of an organism the diastasic 

 action presents the greatest difficulties. In all tests (seven are 

 represented in the group number of the Society's classification 

 card) of the activity of bacteria toward certain substances the 

 aim is accuracy and ease of application. As at present carried 

 out, the diastase test is far from satisfactory, not only because 

 of the difficulty in obtaining potatoes of uniform ciuality, but 

 also because of the difficulty arising when one tries to make a 

 sharp distinction between "strong" and "feeble action." If the 

 action is vigorous or if it is very feeble it is easily classed, but there 

 are points between these extremes which produce doubt and the 

 test then becomes a matter of mere judgment. 



During the last two years in the Dairy Bacteriology Labora- 

 tory of the University of lUinois the use of potato slants for the 

 determination of diastase production by bacteria has been 

 replaced by a simple plate method as follows: A starch agar is 

 made by adding 0.2 per cent of water-soluble stanch to the 

 regular plain agar. This starch agar can be sterilized in the 

 autoclave along with other media. Some hydrolysis takes place, 

 but not enough to interfere with the test. The agar is poured 

 into Petri dishes and allowed to cool, when a stroke 2 inches long 

 is made with a loopful of an agar slant growth of the organism 

 to be tested. The plates are incubated for two days at 37°C. 

 and five days at 20 °C., after which they are flooded with a satu- 

 rated solution of iodine in 50 per cent alcohol. 



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